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Discussion Starter #1
Alright, was hoping it wouldn't come to this...

Got a "quarantine project" ST2. 2002. Friend - of - a - friend "please take this off my hands" deal. Less than 10,000 miles, license plates circa 2012. Says it ran fine when he parked it, I no reason not to believe him. The thing is almost perfect physically.

So everything in the fuel tank assembly was trashed from soaking in what i assume was low-ethanol economy gas. No surprise there, I replaced the seized fuel pump and most of the other stuff in the tank.

Now that I've got the tank back on - the fuel pump doesn't prime and I've got no spark. The pump obviously didn't prime before.

I have:

  • removed the under-seat relays and manually actuated them with a bench power supply
  • manually run the new fuel pump after installation by poking the pins in the under-tank connector with leads straight off the battery
  • checked the three under-seat fuses. (7.5, 7.5, 20 if i recall)
  • measured resistance from what appears to be an obvious ground point on the ECU to a spot of bare metal on the engine block - 0.5 ohms
I do not hear one of the relays under the seat clicking as I would expect for priming. (no 2-3 second on-off).

Right now I think my best bet is to find the "master ground" on the engine block and check its condition. Haven't been able to find it, the master ground off the ECU just sneaks into the wiring harness. (plugs just float on their transformers, right?) I'm not sure if that 0.5 ohms is just due to my cheap meter and leads or is an actual bad connection somewhere - but i'd like to get it to 0 for troubleshooting purposes.

I know for the spark I should check the crank position sensor but the fueling is my first concern right now.
I'm doing my testing with the (functioning) side stand up, center stand down.

So, any more ideas?
thanks
 

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Discussion Starter #2 (Edited)
Did slightly more googling and found the ground point on the transmission housing behind the rear brake fluid reservoir. It looks to be in perfect condition. Jumped this straight to the grounding lug on the ECU and there was no difference in behavior - so i'm ready to rule out "ecu ground fault".
 

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I don’t know much about your specific bike , but when I have had a problem that I thought might be ground related this is what I do: Clean my main ground between battery and frame.
Put a new ground wire from the engine to that main frame ground.
Run a wire from the ECU ground point to that same main frame ground.
This is called ” Single Point Ground” Everything on the bike grounded to one clean ground point, the main battery ground point.
I had a problem with my Busa and just took the whole flippin’ body off until I knew it was fixed. Too much crap in the way.
Whenever I have an electrical problem I always assume corrosion, so I take the time to unplug every connector , clean , lube and tighten them. If they are suspect at all I replac them before they become a problem. This is because I don’t know shit about electrical stuff but I know I’ll have less problems if the connections are clean. It works for me.
 

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Discussion Starter #4
Also can anyone tell me - is the fuel pump supposed to prime when you turn the key or when you flip the kill switch?
 

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2001 900SSie
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just a couple of thoughts.
Disable the side/kick stand function by unplugging the connector and wrap fine wire around all three pins.
That makes sure the stand is sensed as up.
Not sure about the 2002 but the 2000 relays are not all the same, so if you you have one in an incorrect socket you will have problems.
In the 2000 the relay that powers up some of the fuses has two #87 terminals. If you put in in a relay with only one, then some things will not get power.
Same with the injection relay and one other that may be a 'good to go" relay activated by the ECU.
 

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Here is the 2000 wiring schematic.
The blue circled relay is the injection relay.
Relay 48 is the stand relay.
The kill switch will need to be in the run position.
A method to work out which relay or signals to it are causing a problem is to unplug the relay.
Then determine from the relay which socket terminals correspond to 30 and 87.
Then with a short wire in a u shape, insert it to 30 and 87 to make it look like the relay closed.
 

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I would start by checking all teh connections - especially that large one on the left side panel plus the front fuse box. When you turn it ON do the lights all work and horn? Does the starter turn the motor over? Does your model have the immobiliser and if so is it connected (2 pin plug)? Do you have +12v to the main fuse panel and to the main switch and to the Off-Run switch?
 

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there's no frame earths on injected ducati 916>. if the pump is not running it's a dead ecu or ecu power supply. i'd find another ecu to try in it, and rule that out / confirm first up.
 

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Discussion Starter #9
Thanks @Punch for the diagram.

I have now definitely, for sure verified that everything upstream of the injection relay functions correctly and consistently by watching the voltage across pins 85 and 86 of the injection relay while flipping various switches, moving the side stand up and down, etc.

With 12v present on pin 86 of the injection relay and for the (confirmed good) relay to remain open, all that is left in the circuit is the ECU and its main connector. (the ecu must switch a transistor that interrupts current across the relay coil)

I have also verified 0 ohms between injection relay pin 85 and ecu pin 23, as well as 0ohm between injection pin 86 and ecu pin 26.
At this point I think I've done my due diligence in checking everything but the ECU.

Gonna do the "unplug it and plug it back in" approach but if that doesn't help I'll probably crack it open and see if there are any obviously blown smds I can bodge.
Looks like someone's had a go at this before because there's some tape residue that reads "void", the other sticker says 748ducati075, and there's suspicious sharpie writing "ST2 CAL".

there are like two options on ebay which isn't promising.
 

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Discussion Starter #10
OK last call before I go ripping apart my ECU. No more gotchas like the sidestand?
I'm pretty dang sure the ECU just plain isn't switching that relay but don't wanna believe it because the thing has spent the last 20 years in a garage.
 

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Do you mean relay 48 in the diagram? That is switched by the side stand switch 35.
Just pull the relay and test voltage across 85 and 86 when the stand is up.
If there is no voltage but want to move forward quickly, just use a bit of wire to connect socket terminals 30 and 87 to bypass the stand function.
 

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Discussion Starter #12
Its not the sidestand. I've manually tested the sidestand switch, the sidestand relay, and have verified 12v at the coil of the injection relay, which indeed is switched properly when i move the sidestand, and rules out everything upstream. I've also jumped the injection relay and the pump does run.
 

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There is another relay to the left of the injection relay. Not sure what that does.
I do not know what each ECU pin does.
 

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Discussion Starter #14 (Edited)
cracked open the ECU. There was a solder blob rattling around in there. Maybe that was shorting something, I'm doubtful though since the board is coated. Otherwise upon careful inspection the board appears perfect.

One strange clue though - the eprom chip has definitely been tampered with or possibly replaced before - its silicone blob and tape were broken. It's not an "upgraded" chip as far as I can tell - just says "ST2 cal".

So my new theory is that something about this bike or the previous owner has been killing these chips...
He did give me a junk charger when he sold me the ST2. I haven't used it because it doesn't seem trustworthy - I wouldn't be surprised if thats the culprit.

so i'll put the ecu back on this weekend and see if by luck if was the solder blob. perhaps i'll poke around with a scope for fun. next thing i'll try is to watch ebay for a stock st2 eprom.

Oh and isn't there a way to read diagnostic codes on these bikes? I wouldn't be at all surprised if my water temp sensor is shorted to ground or something and putting the ECU in a fail-safe mode. I thought I read something about a flashing light that you hook up somewhere but i can't find it again. if there's just a pin in a connector somewhere thats going high and low i could probably just record that on a scope without the special tool.

edit: ah, i remembered last night that this is apparently a 748 ECU. that would explain why the chip would have been swapped
 
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